KR101720960B1 - Apparatus and Method For Equalizing Charge of a Battery Pack - Google Patents

Abstract

The present invention relates to an apparatus and a method to equally charge a battery pack by variably controlling balancing current in accordance with a voltage difference between battery cells. According to the present invention, the apparatus comprises: a charger to supply charging current to multiple battery cells connected in series; a voltage monitoring unit to monitor cell voltage of the battery cells; a balancing unit including a balancing resistor and a balancing transistor connected to each battery cell in parallel; an integrated control unit receiving the cell voltage measured by the voltage monitoring unit to determine a battery cell to be balanced and a balancing current level, and controlling base current of the balancing transistor connected to the battery cell to be balanced in accordance with the determined balancing current level; and a charging current control unit controlled by the integrated control unit to decrease the charging current outputted from the charger when balancing is performed.

Description

TECHNICAL FIELD [0001] The present invention relates to a balancing current variable battery pack,

The present invention relates to a battery pack equalizing apparatus and method, and more particularly, to an apparatus and method for uniformly charging a battery pack by varying and balancing a balancing current according to a voltage difference between battery cells.

Generally, the secondary battery includes a nickel cadmium battery, a nickel metal hydride battery, a lithium ion battery, and a lithium ion polymer battery. Such a secondary battery is classified into a lithium-based battery and a nickel-hydrogen-based battery.

In the case of an ESS (Energy Storage System) system and an electric vehicle that require a high power source, a plurality of battery cells connected in series are used as a package. Each battery cell constituting the battery pack has a voltage difference between battery cells due to chemical difference, physical property difference, and the like. Particularly, since the degree of deterioration of the battery cells is different as the charge and discharge continues and deteriorates, the charge-discharge time and the charge-discharge amount of each battery cell are different. The battery cell having a relatively large deterioration has a shorter charging / discharging time than other cells, and therefore, the battery cell first becomes fully charged or discharged. In addition, the battery cells whose degradation is relatively less advanced terminate the charging or discharging before full charge or full discharge.

When the battery cell is continuously charged and discharged, the deterioration degree of the deteriorated battery cell becomes worse, and the cell voltage of the battery cell having a low voltage becomes lower. As a result, it may cause ignition or explosion of the secondary battery, and the entire battery pack must be replaced due to the unit battery cell, resulting in an economical loss.

To solve this problem, battery cell balancing is applied to the battery pack. Battery cell balancing refers to charging while maintaining the voltage difference between the series-connected battery cells within a predetermined range. As a conventional battery cell balancing method, a passive cell balancing method of a discharging type by resistance and an active type cell balancing method by a DC converter are widely known.

Meanwhile, FIG. 1 shows a charge characteristic curve and a discharge characteristic curve of a lithium iron phosphate battery. As the charge progresses, when 10% of the battery capacity is charged, the output rises to 3.2V (referred to as the 'low voltage rise interval') and most of the capacity above the 85% range in the 3.2V to 3.4V voltage range is charged (This is referred to as a 'flat section'). In order to recover the remaining 15% capacity, the voltage rises sharply to 3.9V (this is called the 'high voltage rise interval'). That is, as the lithium iron phosphate battery is charged, full charge progresses through the low voltage rising section, the flat section, and the high voltage rising section.

In a conventional passive cell balancing method, when a cell voltage is measured in real time and a maximum voltage is equal to or higher than a balancing voltage (typically 3.7 V), the battery cell voltage is discharged through a discharge resistor of a fixed size, Perform balancing. However, when the balancing voltage belongs to the high voltage rising period or the voltage difference between the highest cell voltage and the lowest cell voltage is large, since the amount of balancing current with respect to the charging current amount is very small, the battery cell is discharged by discharging the balancing current, There is a problem that the voltage charged by the charging current is greater than the voltage discharged by the balancing current, and consequently the battery cell voltage continuously increases.

International Publication WO2012-124845 Japanese application JP2008-233966 Japanese application JP2003-413965

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art, and it is an object of the present invention to provide a battery pack having a high- The present invention is to provide a battery pack equalizing apparatus and method for performing cell balancing while varying the cell balancing efficiency in conjunction with a charging current.

It is another object of the present invention to provide a battery pack equalizing apparatus and method for measuring the collector voltage of a balancing transistor while controlling the amount of balancing current to diagnose the failure of the balancing transistor.

According to an aspect of the present invention, there is provided a battery pack equalizing apparatus including a charger for supplying a charging current to a plurality of battery cells connected in series,

A voltage monitoring unit for sensing a cell voltage of the battery cell;

A balancing unit including a balancing resistor and a balancing transistor connected in parallel to each of the battery cells,

An integration controller for receiving a cell voltage measured by the voltage monitor to determine a battery cell to be balanced and an amount of balancing current and controlling a base current of a balancing transistor connected to the battery cell to be balanced according to the determined amount of balancing current,

And a charge current controller for reducing the charge current outputted from the charger when performing balancing under the control of the integrated controller.

According to another aspect of the present invention, there is provided a battery pack equalizing method, comprising: a charger for supplying a charging current to a plurality of battery cells connected in series; a voltage monitoring unit for sensing a cell voltage of the battery cell; A balancing unit configured by resistors and balancing transistors, an integration controller for receiving battery voltage measured by the voltage monitor, and performing battery balancing, and a control unit for controlling the charge current And a charging current control unit for reducing the charging current of the battery pack,

A first step of the integrated controller receiving a battery cell voltage measured by the voltage monitoring unit and determining a balance battery cell and a balancing current amount,

A second step of controlling the charge current control unit to reduce the charge current when the integrated control unit determines the balancing target battery cell in the first step;

And a third step of controlling the base current of the balancing transistor connected to the balancing target battery cell according to the balancing current amount determined in the first step.

As described above, according to the present invention, in the cell balancing operation, when the charging current is reduced while interlocking with the charger, whether or not the highest cell voltage enters the high voltage rising period, and whether the base voltage of the balancing transistor The balancing effect is maximized because the amount of balancing current is varied by adjusting the current.

Further, it is advantageous to diagnose the failure of the balancing transistor by measuring the collector voltage of the balancing transistor while controlling the balancing current amount.

1 is a graph showing a charging characteristic curve and a discharge characteristic curve of a lithium iron phosphate battery.
2 is a block diagram illustrating a battery charging system including a battery balancing apparatus according to the present invention.
3 is a flowchart showing the operation of the integrated control unit according to the present invention.

Hereinafter, a battery pack equalizing apparatus and method according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram illustrating a battery charging system including a battery balancing apparatus according to the present invention.

The battery charging system according to the present invention includes a charger 12 for supplying a charging current to a plurality of battery cells 11A and 11B connected in series, a voltage monitoring unit 13 for sensing a cell voltage of the battery cell, An integrated controller 14 for receiving a cell voltage measured by the voltage monitor 13 and determining whether to balance the battery voltage and detecting a balancing target, and a balancing resistor 15A, 15B connected in parallel to each of the battery cells 11A, And a balancing unit composed of balancing transistors 16A and 16B and a digital control signal for controlling the base currents of the balancing transistors 16A and 16B connected to the battery cells to be balanced under the control of the integrated control unit 14. [ A DAC 18A and 18B for converting the digital control signal into an analog signal and supplying the digital control signal to the base currents of the balancing transistors 16A and 16B; Or measurement point selection switches 19A and 19B for selecting one of the common points of the balancing resistor and the balancing transistor and connecting the measurement point to the voltage monitoring unit 13, A measuring point selection unit 20 for controlling the measurement point selection switches 19A and 19B and a control unit 20 for controlling the charging and discharging operations of the plurality of battery cells And a charge current control unit 21 for reducing the current. In addition, the battery charging system according to the present invention further includes a current sensing unit 22 for sensing the magnitude of the charging current supplied to the plurality of battery cells in the charger 12.

The operation of the battery charging system and the battery balancing device constructed as described above will be described.

The charger 12 generates a charging current and supplies it to the plurality of battery cells 11A and 11B connected in series, and the plurality of battery cells 11A and 11B are charged by the charging current. The voltage monitoring unit 13 senses the cell charging voltage of each battery cell and provides the integrated control unit 14 with the detected cell voltage information of each battery cell.

Based on the cell voltage information of the battery cell, the integrated controller 14 determines whether or not the battery is to be balanced, determines a balancing object and a balancing current amount, and performs a balancing operation based on the balancing current amount with respect to the object to be balanced. The balancing current amount is determined based on whether or not the maximum cell voltage has entered the high voltage rising period and the voltage difference between the maximum cell voltage and the minimum cell voltage.

The integrated controller 14 determines whether or not to balance based on the cell voltage information of the battery, and determines the balancing object and the balancing current amount. When the balancing object is detected, the integrated controller 14 controls the charge current controller 21 to output a signal to the charger 12 so that the charge current supplied to the battery cells 11A and 11B in the charger 12 is .

At the same time, the integrated control unit 14 controls the balancing current regulating unit 17 to regulate the balancing current of the balancing subject battery cell (for example, assuming the first battery cell 11A). The balancing current control unit 17 determines the balancing current amount of the battery cell to be balanced based on the determined amount of balancing current. The balancing current control unit 17 controls the balancing current of the first battery cell 11A. And outputs a digital control signal. The DAC 18A converts the digital control signal to analog and outputs it as the base current of the balancing transistor 16A. Then, the amount of balancing current flowing to the balancing resistor 15A is adjusted according to the base current of the balancing transistor 16A, and the discharging rate of the charging voltage of the battery cell is changed according to the balancing current.

On the other hand, when the battery cell voltage is measured, the integrated controller 14 allows the measurement point selection switch 19A to select the common contact point between the battery cell 11A and the balancing resistor 15A, The selection switch 19A selects the common contact of the balancing resistor 15A and the balancing transistor 16A. When the measurement point selection switch 19A selects the common point of the balancing resistor 15A and the balancing transistor 16A, the voltage monitoring section 13 can measure the collector voltage of the balancing transistor 16A. The measurement point selection operation of the measurement point selection switch 19A is performed by the measurement point selection unit 20 under the control of the integrated controller 14. [

At the time of diagnosis of the balancing part failure, the voltage monitoring part 13 measures the collecting voltage of the balancing transistor 16A. The integrated controller 14 measures the collector voltage of the balancing transistor 16A while controlling the base current of the balancing transistor 16A so that the amount of balancing current is maximized and if the collector voltage is not decreased, do. The integrated controller 14 also measures the collector voltage of the balancing transistor 16A while controlling the base current of the balancing transistor 16A such that the amount of balancing current is at an intermediate value and if the collector voltage is zero, ) Is short-circuited.

3 is a flowchart showing the operation of the integrated control unit according to the present invention.

The integrated controller 14 senses the cell voltage of each battery cell through the voltage monitoring unit 13 to determine whether to balance or not, and determines the balancing object and balancing current amount (S31). Here, the balancing current amount is determined based on whether or not the maximum cell voltage has entered the high voltage rising period and the voltage difference between the maximum cell voltage and the minimum cell voltage. As the voltage difference increases, the amount of balancing current increases. As the voltage difference decreases, the balancing current decreases. When the maximum cell voltage enters the high voltage rising period, the balancing current increases.

The integrated controller 14 controls the charge current controller 21 to reduce the charge current supplied from the charger 12 to the plurality of battery cells 11A and 11B during the balancing operation S32.

The integrated controller 14 controls the base current of the balancing transistor connected to the battery cell to be balanced according to the balancing current amount determined in step S31 (S33). The amount of balancing current flowing through the balancing resistor is determined according to the base current of the balancing transistor, and the discharge speed of the battery cell to be balanced is determined accordingly. According to the present invention, when the voltage difference between the highest cell voltage and the lowest cell voltage is high or when the highest cell voltage enters the high voltage rising period, the balancing current amount is increased to increase the discharging speed of the battery cell, thereby quickly performing cell balancing .

Further, the integrated controller 14 periodically or, if necessary, diagnoses the failure of the balancing transistor. The integrated control unit 14 controls the voltage monitoring unit to measure the collector voltage of the balancing transistor by selecting the common point of the balancing resistor and the balancing transistor.

The integrated controller 14 measures the collector voltage of the balancing transistor while controlling the base current of the balancing transistor so that the amount of balancing current is maximized. If the collector voltage is not decreased, the integrated controller 14 determines that the balancing transistor is broken. In addition, the integrated controller 14 measures the collector voltage of the balancing transistor while controlling the base current of the balancing transistor so that the balancing current amount is at an intermediate value, and determines that the balancing transistor is short-circuited if the collector voltage is zero (S36 ).

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. In addition, it is a matter of course that various modifications and variations are possible without departing from the scope of the technical idea of the present invention by anyone having ordinary skill in the art.

11A, 11B: battery cell 12: charger
13: Voltage monitoring unit 14: Integrated control unit
15A, 15B: Balancing resistors 16A, 16B: Switching elements
17: balancing current regulating section 18A, 18B: DAC
19A, 19B: Measurement point selection switch 20: Measurement point selection section
21: charge current control unit 22: current sensing unit

Claims (9)

A charger for supplying a charging current to a plurality of battery cells connected in series;
A balancing unit including a balancing resistor and a balancing transistor connected in parallel to each of the battery cells;
A voltage monitoring unit for measuring a cell voltage of the battery cell or a collector voltage of the balancing transistor;
And a control unit for controlling the base current of the balancing transistor connected to the battery cell to be balanced according to the determined amount of balancing current, And an integrated controller for measuring a collector voltage of the balancing transistor to diagnose the failure of the balancing transistor,
Wherein the integrated controller measures a collector voltage of the balancing transistor while controlling a base current of the balancing transistor so that the balancing current amount is maximized and determines that the balun is broken if the collector voltage is not decreased Battery pack equalization device. A charger for supplying a charging current to a plurality of battery cells connected in series;
A balancing unit including a balancing resistor and a balancing transistor connected in parallel to each of the battery cells;
A voltage monitoring unit for measuring a cell voltage of the battery cell or a collector voltage of the balancing transistor;
And a control unit for controlling the base current of the balancing transistor connected to the battery cell to be balanced according to the determined amount of balancing current, And an integrated controller for measuring a collector voltage of the balancing transistor to diagnose the failure of the balancing transistor,
Wherein the integrated controller measures a collector voltage of the balancing transistor while controlling a base current of the balancing transistor so that the balancing current amount is an intermediate value and determines that the balancing transistor is short-circuited if the collector voltage is zero Battery pack equalization device. The apparatus according to claim 1 or 2, further comprising a measurement point selection unit for controlling the voltage of the voltage monitoring unit to be a cell voltage of the battery cell or a collector voltage of the balancing transistor under the control of the integrated controller Of the battery pack. The apparatus of claim 1 or 2, further comprising a charge current controller for reducing the charge current output from the charger when performing balancing under the control of the integrated controller. The apparatus of claim 1 or 2, further comprising a current sensing unit for sensing a magnitude of a charging current supplied to the plurality of battery cells in the charger. A charger for supplying a charging current to a plurality of battery cells connected in series; A balancing unit including a balancing resistor and a balancing transistor connected in parallel to each of the battery cells; A voltage monitoring unit for measuring a cell voltage of the battery cell or a collector voltage of the balancing transistor; And a control unit for controlling the base current of the balancing transistor connected to the battery cell to be balanced according to the determined amount of balancing current, And an integrated controller for measuring a collector voltage of the balancing transistor and diagnosing whether the balancing transistor is faulty, the method comprising:
The integrated control unit receiving the battery cell voltage measured by the voltage monitoring unit and determining a balance battery cell and a balancing current amount,
Controlling the base current of the balancing transistor connected to the balancing target battery cell according to the determined balancing current amount;
And diagnosing a failure of the balancing transistor by measuring a collector voltage of the balancing transistor while the integrated controller controls a base current of the balancing transistor,
In the failure diagnosis step, the integrated controller measures the collector voltage of the balancing transistor while controlling the base current of the balancing transistor so that the balancing current amount is maximized. If the collector voltage is not decreased, Wherein the battery pack is a battery pack. A charger for supplying a charging current to a plurality of battery cells connected in series; A balancing unit including a balancing resistor and a balancing transistor connected in parallel to each of the battery cells; A voltage monitoring unit for measuring a cell voltage of the battery cell or a collector voltage of the balancing transistor; And a control unit for controlling the base current of the balancing transistor connected to the battery cell to be balanced according to the determined amount of balancing current, And an integrated controller for measuring a collector voltage of the balancing transistor and diagnosing whether the balancing transistor is faulty, the method comprising:
The integrated control unit receiving the battery cell voltage measured by the voltage monitoring unit and determining a balance battery cell and a balancing current amount,
Controlling the base current of the balancing transistor connected to the balancing target battery cell according to the determined balancing current amount;
And diagnosing a failure of the balancing transistor by measuring a collector voltage of the balancing transistor while the integrated controller controls a base current of the balancing transistor,
In the fault diagnosis step, the integrated controller measures the collector voltage of the balancing transistor while controlling the base current of the balancing transistor so that the balancing current amount is at an intermediate value. If the collector voltage is zero, Wherein the battery pack is a battery pack. The method according to claim 6 or 7, further comprising the step of causing the integrated controller to reduce the charging current when the balancing current amount and the balancing current amount are determined. 8. The method of claim 6 or 7, further comprising the step of the integrated controller selecting a measurement point such that the measured voltage of the voltage monitoring unit is the battery cell voltage or the collector voltage of the balancing transistor Charging method.

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